Cataract is apparently associated with an irreversible aberration in the lens fiber cell, and perhaps a reversible defect in the metabolism of the lens epithelial cell. Numerous biochemical changes are associated with cateracts, e.g., protein loss and protein degradation in fiber cells, hyperosmolarity of the cortex, and amino acid degradation. There is also degeneration of lens fibers followed by proliferation and migration of the epithelial cells from the equator leading to epithelial cell enlargement and reduction in their nuclear mass. We hypothesize that some dysfunction in the lens fiber cell membrane may underly some of these biochemical and cellular changes. This proposal is designated to elucidate whether specific components of the lens fiber cell are changed during cateract development. To this end we have chosen to study the expression of the gene for the main intrinsic protein (MIP or MP26) of fiber cell membranes in normal bovine, rat or mouse lens and in cataractous lens of the Nakano mouse, and those of rats in which cataractogenesis has been induced by galactose or reversed by removal of galactose from the diet. Parallel studies will also be carried out on human normal and cataractous lenses. We are proposing to use new techniques of molecular biology in these proposed studies on the MP26 gene. Briefly, the main intrinsic protein, MP26, will be isolated to homogeneity, its antisera will be produced in rabbits, and its mRNA will be probed for by an MP26 clone, prepared in this laboratory, in order to follow the expression of the MP26 gene in lens undergoing different experimental conditions. These methods will include the preparation of a lens cDNA library in expression vectors for the immuno-identification of MP26 positive clones or any other desired clones. The MP26 clone will then be amplified and used for the proposed studies on the expression of the MP26 gene. It is expected that these studies will show how a specific fiber cell mRNA is modulated during cataractogenesis.